Cochlear implants are highly successful neural prostheses that enhance or restore hearing to the severely hearing impaired. However, performance varies considerably among cochlear implant listeners, particularly in noisy environments and for spectrally complex stimuli like music. Pathology and imaging studies suggest that two sources of performance variability are the distribution of surviving spiral ganglion neurons and their distance from individual CI electrodes. This proposal uses psychophysical measures, computed tomography imaging, and computer modeling to assess how such factors affect the function of individual cochlear implant channels. That information will be applied to reprogram the implant processor in order to minimize the influence of poorly functioning channels. Three aims are proposed: 1) To determine the degree to which thresholds obtained using a spatially focused electrode configuration correlate with single-channel measures of spectral resolution, loudness growth, and electrode position within the cochlea; 2) To quantify the contributions of channels with high thresholds on the discrimination of speech stimuli; and 3) To determine if listener-specific mapping tailored to the estimated electrode-neuron interface from Aim 1 can improve perception on complex listening tasks. The results of these studies are expected to advance the field's understanding of how cochlear implant channel position and neural survival affect single-channel and speech perception. The findings have the potential to shift clinical practice by providing a guide for patient-specific channel mapping and ultimately lead to improved speech perception abilities in cochlear implant listeners. PUBLIC HEALTH RELEVANCE: A cochlear implant converts environmental sounds into electrical pulses that stimulate the auditory nerve and produce the sensation of hearing in people with severe hearing loss. The primary purpose of this project is to develop better tools for testing cochlear implant function within individual listeners, and to apply that knowledge to develop new implant fitting techniques to improve listening performance.